A generic feature of transition rates in field theory is that they are exponentially staggered. This is because rates depend exponentially on the shape of the potential, such as the height and width of the barrier. Hence branching ratios are typically overwhelmingly dominated by a single decay channel, while other decay channels are comparatively exponentially suppressed.There are of course exceptions, for instance in regular lattices of flux vacua [1]}, but one expects that single-channel dominance is justified for random landscapes.
